Materials Library

UO₂

Uranium dioxide at 3 wt% U-235 enrichment. Standard fuel for commercial PWRs and BWRs. This is the compendium's own UO₂ entry, whose uranium is 3.0 wt% enriched.

ρ = 10.96 g/cm³ · PNNL-15870

UO₂

Uranium dioxide at 4.5 wt% U-235 enrichment. Common in high-burnup PWR fuel assemblies.

ρ = 10.96 g/cm³ · derived recipe

UO₂

Uranium dioxide at 5 wt% U-235 enrichment. The licensing ceiling for standard commercial fuel in the United States.

ρ = 10.96 g/cm³ · derived recipe

UO₂

Uranium dioxide at 19.75 wt% U-235 — high-assay low-enriched uranium, the working fuel of most advanced reactor and research reactor designs.

ρ = 10.96 g/cm³ · derived recipe

(U,Pu)O₂

Mixed-oxide fuel: reactor-grade plutonium in a depleted-uranium matrix (0.25 wt% U-235). Plutonium is 4.7 wt% of the heavy metal.

ρ = 11 g/cm³ · PNNL-15870

UN

Uranium mononitride at 3 wt% U-235. High uranium density and high thermal conductivity make it attractive for advanced and space reactors.

ρ = 14.31 g/cm³ · PNNL-15870

UC

Uranium monocarbide at 3 wt% U-235. High heavy-metal density and good thermal properties for fast and space reactor fuel.

ρ = 13.63 g/cm³ · PNNL-15870

UZrH₁.₆

Uranium–zirconium hydride fuel used in TRIGA research reactors. The hydride matrix is what gives TRIGA its large prompt negative temperature coefficient.

ρ = 5.97 g/cm³ · derived recipe

Zirconium alloy cladding used in BWRs. Low absorption cross section with good corrosion resistance.

ρ = 6.56 g/cm³ · PNNL-15870

Zirconium alloy cladding used in PWRs. No nickel, which improves hydrogen pickup resistance in PWR coolant chemistry.

ρ = 6.56 g/cm³ · PNNL-15870

Austenitic stainless steel used for reactor structural components, piping, and vessel internals.

ρ = 8.03 g/cm³ · PNNL-15870

Molybdenum-bearing austenitic stainless steel with improved corrosion resistance. Used in fast reactor cladding, PWR internals, and hot-leg piping.

ρ = 8 g/cm³ · PNNL-15870

Nickel–chromium superalloy used in vessel head penetrations, springs, and high-temperature structure.

ρ = 8.19 g/cm³ · PNNL-15870

Nickel–molybdenum alloy developed for molten-salt service. The structural material of the MSRE and of most proposed MSR designs.

ρ = 8.86 g/cm³ · derived recipe

Plain medium-carbon steel, for structural supports, containment liner, and shielding geometry where the exact alloy does not matter.

ρ = 7.872 g/cm³ · PNNL-15870

H₂O

Room-temperature light water — moderator and coolant in PWRs and BWRs.

ρ = 0.997 g/cm³ · PNNL-15870

D₂O

Deuterium oxide at room temperature — moderator and coolant in CANDU and other heavy-water reactors, where the neutron economy allows natural-uranium fuel.

ρ = 1.1044 g/cm³ · PNNL-15870

C

Nuclear-grade graphite moderator, for gas-cooled reactors (AGR, HTGR), RBMK, and molten-salt designs.

ρ = 1.7 g/cm³ · PNNL-15870

Be

Beryllium metal reflector and moderator for research and test reactors. Excellent neutron economy, and Be-9(n,2n) makes it a multiplier as well as a reflector.

ρ = 1.848 g/cm³ · PNNL-15870

BeO

Beryllia moderator and reflector for compact reactors. Denser than graphite with excellent thermal conductivity.

ρ = 3.01 g/cm³ · PNNL-15870

Li₂BeF₄

Lithium fluoride–beryllium fluoride molten salt, the coolant and fuel carrier of fluoride-salt-cooled and molten-salt reactors.

ρ = 1.94 g/cm³ · derived recipe

LiF-NaF-KF

Lithium–sodium–potassium fluoride eutectic, used as a secondary coolant and heat-transfer salt in molten-salt designs.

ρ = 2.09 g/cm³ · derived recipe

Na

Sodium coolant for sodium-cooled fast reactors — EBR-II, BN-600/800, Natrium.

ρ = 0.971 g/cm³ · PNNL-15870

Pb

Natural lead coolant for lead-cooled fast reactors, and a workhorse gamma shield.

ρ = 11.35 g/cm³ · PNNL-15870

Pb-Bi

Lead–bismuth eutectic: a liquid-metal coolant for fast reactors and spallation targets, melting at about 125 °C instead of lead's 327 °C.

ρ = 10.17 g/cm³ · derived recipe

CO₂

Carbon dioxide at room conditions — coolant in Magnox and AGR reactors, and the working fluid of supercritical CO₂ power cycles.

ρ = 0.00184212 g/cm³ · PNNL-15870

He

Helium at room conditions — HTGR and VHTR coolant, and the fill gas in a fuel-cladding gap.

ρ = 0.000166322 g/cm³ · PNNL-15870

Portland cement concrete — the primary biological shield in most reactor facilities.

ρ = 2.3 g/cm³ · PNNL-15870

High-density concrete with baryte (BaSO₄) aggregate, for gamma shielding where thickness is limited.

ρ = 3.35 g/cm³ · PNNL-15870

(CH₂)ₙ + B

Polyethylene loaded with 10 wt% natural boron: hydrogen slows the neutrons down and B-10 absorbs them, in one material.

ρ = 1 g/cm³ · PNNL-15870

(CH₂)ₙ

High-density polyethylene — the densest practical hydrogen source, and so an efficient neutron shield per centimetre.

ρ = 0.93 g/cm³ · PNNL-15870

B₄C

Boron carbide with natural boron (19.9 at% B-10) — control rod and shutdown absorber, and the most common burnable absorber outside the fuel.

ρ = 2.52 g/cm³ · PNNL-15870

B₄C

Boron carbide enriched to 90 at% B-10, for control rods and shields that need maximum absorption per unit volume.

ρ = 2.393 g/cm³ · derived recipe

Ag-In-Cd

Silver–indium–cadmium alloy, the standard PWR control rod absorber. Absorbs across a wide energy range instead of relying on one resonance.

ρ = 10.17 g/cm³ · derived recipe

Gd₂O₃

Gadolinia burnable absorber, usually mixed into UO₂ pellets at a few weight percent. Gd-155 and Gd-157 have the largest thermal capture cross sections of any stable nuclides.

ρ = 7.41 g/cm³ · derived recipe

Hf

Hafnium metal control rod absorber. Used where a rod has to last: successive captures walk through the isotope chain and every step still absorbs.

ρ = 13.31 g/cm³ · derived recipe

Eu₂O₃

Europia control and burnable absorber material, used in Russian reactor designs and in research reactor control elements.

ρ = 7.42 g/cm³ · derived recipe

Dry air near sea level, for streaming paths, room modelling, and atmospheric transport.

ρ = 0.001205 g/cm³ · PNNL-15870

Ar

Argon at room conditions — cover gas above sodium in an SFR, where it keeps air away from the coolant.

ρ = 0.00166201 g/cm³ · PNNL-15870

N₂

Nitrogen at room conditions, for inerting containment and fuel handling areas.

ρ = 0.00116528 g/cm³ · PNNL-15870

Vacuum or void region: no material, and particles stream through without interacting.

no material